1. Field of the Invention
The present invention relates to an amplifying circuit, and more particularly, relates to an amplifying circuit including a differential amplifier.
2. Description of the Related Art
A driver for driving a display panel, such as liquid crystal display panels, includes a plurality of amplifiers each configured to apply gradation voltages to data lines of the liquid crystal display panel. The gradation voltages have voltage values corresponding to the luminance levels indicated by an input video signal.
As one of such amplifiers, a differential amplifier which is configured to output one gradation voltage and includes differential pairs of two systems that receive inputs of these two systems, respectively is proposed (see, for example, Japanese Patent Application Laid-Open No. 2005-130332). Such a differential amplifier can output not only gradation voltages of these two systems but also gradation voltages of additional two systems larger (or smaller) than the former voltages obtained by combining these former input gradation voltages.
As the resolution of the liquid crystal display panels is getting higher in recent years, the amplifiers of the driver are expected to have a high speed response and a high current output. However, in order to enhance the output current of the differential amplifier, it is necessary to upsize transistor elements in differential stages that form the differential amplifier. This increases an input capacitance and decreases a response speed in proportion to the upsizing.